Question

Resistance of a conductivity cell filled with a solution of an electrolyte of concentration 0.1M is 100$\Omega$. The conductivity of this solution is 1.29$S{m}^{-1}$. Resistance of the same cell when filled with 0.02M of the same solution is 520$\Omega$. The molar conductivity of 0.02M solution of the electrolyte will be.
(1) $124\times {10}^{-4}{Sm}^2{}^{-1}$
(2) $1240\times {10}^{-4}{Sm}^2{}^{-1}$
(3) $1.24\times {10}^{-4}{Sm}^2{}^{-1}$
(4) $12.4\times {10}^{-4}{Sm}^2{}^{-1}$

Answer 1

The correct option is D.

Given,

Concentration +0.1mis 100ohm$

$conductivity=1.29s{m}^{-1}$

Resistance os $0.2mis520ohm$

So,

Cell constant can be determined by the $0.1mkcl$

$=k\times R$

$0.0129\times 100$

$1.29$

So, the conductivity of the $0.2mkcl$ is:

Cell constant is divided by the resistance,

$\frac{1.29}{520}=2.48\times {10}^{-3}$

Therefore the molar conductivity is

$\Delta m=\frac{{10}^{3}k}{m}$

$\frac{{10}^3\times 2.48\times {10}^{-3}}{0.02}$

$=1245c{m}^2/mol$

$=12.4\times {10}^{-4}m/mol$